The invention relates to an arrangement for open-end friction spinning with two adjacently arranged friction rollers forming a wedge-shaped gap provided for the yarn formation. The rollers include a drive arrangement which drives the friction rollers in the same rotational direction. A suction device holds the producing yarn within the wedge-shaped gap. Also included is a member which separates the rollers from the drive arrangement which is controlled by a yarn monitor or detector.
In a known arrangement of the above-indicated type, it is left to chance as to how the rollers react upon separation from the drive arrangement such as which roller is delayed faster or stronger and which roller reduces its speed faster.
It is also disclosed in German Published Unexamined Patent Appliction (DE-OS) No. 33 17 368 to provide an intermediary drive in the form of an endless belt for the two rollers in an open-end friction spinning arrangement. The drive action is derived from a continuous tangential belt. This arrangement further provides that upon discontinuance of the operation of the rollers, the tangential belt is separated from the intermediary drive and a brake member of a deflection roller of the intermediary drive is assigned. With this arrangement it is left to chance as to how the two rollers slow down and come to a standstill. In particular, speed differences could occur between the two rollers up until they have come to a standstill. Speed differences could also occur after the separation from the tangential belt, due to elongation of the endless belt of the intermediate drive.
It is also disclosed in commonly assigned U.S. patent application Ser. No. 662,557, filed Oct. 19, 1984 now U.S. Pat. No. 4,612,762, to provide a cleaning device which can shut off the suction into the wedge-shaped gap for a cleaning process. In this patent application, it is also shown to reverse the direction of one of the rollers in order to free the yarn forming region. This is done by providing rollers which engage the friction spinning rollers during the cleaning process after the driving belt has been removed from the friction rollers.
It is an object of this invention to design an arrangement of the kind mentioned above such that the slowing down characteristics of the two rollers upon separation from the drive is controlled in a predetermined manner.
This object is achieved according to the invention by providing means that control the slowing down characteristics of the rollers upon separation from their drive in such a manner that the friction roller rotating into the wedge-shaped gap does not rotate faster, at least in the area of the high rotational speeds, than the roller rotating out of the wedge-shaped gap.
Normally, during a yarn break, yarn or fiber residues remain in the area of the wedge-shaped gap which may no longer be withdrawn after a yarn breakage and which twist themselves together into a so-called yarn cocoon. The danger then exists that the yarn cocoon may be drawn deeper into the wedge-shaped gap and may get jammed in the same. This sort of jamming in turn creates the danger of damage to the surfaces of the rollers and/or their bearings. It was realized with the invention that the yarn cocoon being drawn deeper into the wedge-shaped gap and thereby creating a jamming can be avoided with more certainty if the roller rotating into the wedge-shaped gap does not run faster, even after separation from the drive, than the roller rotating out of the wedge-shaped gap. The danger of jamming of the yarn cocoon within the wedge-shaped gap is especially high if the two rollers still rotate with relatively high speeds, such as at the time immediately following the separation of the rollers from the drive. In most cases it will therefore be sufficient to limit the control of the slowing down characteristics of the rollers in the range of relative high speeds according to certain preferred embodiments of the invention.
In a further development of preferred embodiments of the invention, it is provided that the two friction rollers are connected with each other by way of a synchronizing means at least immediately upon separation from the drive. In this manner it is more certainly guaranteed that the roller rotating into the wedge-shaped gap does not rotate faster than the roller rotating out of the wedge-shaped gap during the slowing down period.
In another development of preferred embodiments of the invention, means are provided for reducing the speed of, or bringing to a standstill, the roller that rotates out of the wedge-shaped gap, subsequent to reducing the speed of or bringing the roller that rotates into the wedge-shaped gap to a standstill.
In a further development of certain preferred embodiments of the invention, means are provided for switching off the suction device. Thereby it is preferably provided to control the means for switching off the suction device by the yarn detector or monitor. Therefore the air streams or currents are switched off which hold the yarn cocoon in the area of the wedge-shaped gap so that the cocoon can easily be removed from the area of the wedge-shaped gap.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which shows, for purposes of illustration only, several embodiments constructed in accordance with the present invention.